1. Field of the Invention
The present invention relates to flow monitors in general and to a gravity fed volumetric controller and a urinary output monitor, each having an enhanced drop size determination technique including an improved lensing capability necessary to make for simplified drop collection and determination, in particular.
2. Background of the Invention
In the development of fluid flow monitors, the first flow monitors were simply drop recorders, known as drop counters, and now are known as flow rate monitors and controllers. Certain flow rate monitors are used to monitor the production of urine by a patient. Other flow rate monitors are used to monitor and control the introduction of fluids into a patient as by IV infusion. In addition there are mechanical and electronic infusion pumps and controllers used today for parenteral and enteral use.
Basically, there are three categories of devices for IV infusion: gravity IV administration systems, infusion controllers, and infusion pumps.
Gravity IV administration systems utilize a traditional bag or bottle containing a fluid or drug and a flexible administration set. Typically, the flow control of the set is governed by a manual clamp of the screw or roller type. The height of the bottle provides a pressure head that allows the fluid to overcome venous pressure and permits the drug to enter the venous system. However, in recent years, gravity systems have been reviewed for efficacy because of inaccuracies in flow rate.
Infusion controllers, like IV systems, work by gravity and exert no pressure. The controllers count drops electronically and extrude volumes of fluid mechanically and electronically. Because they have relatively few moving parts, infusion controllers are less complex than infusion pumps and are usually less expensive and have fewer maintenance problems.
Infusion controllers may be classified in two groups: volumetric and non-volumetric. In a non-volumetric controller, accuracy is determined by drop rate. The major difference from the traditional IV set is that in a volumetric controller, control of flow is regulated automatically rather than manually.
Infusion pumps differ from the other methods discussed in that they do not depend on gravity to provide the pressure required to infuse the drug. Pressure is provided by an electric pump motor that propels a syringe, a parasystolic or roller device, or a refillable chamber calibrated to deliver a prescribed volume. Most pumps are volumetric and may be adjusted to deliver a drug under different pressures. Among the problems associated with infusion pumps are air embolism occurring despite the use of filters, IV solution bags running dry, clogged catheters, infiltration, extravasation of fluids, phlebitis, and painful IV sites.
Recently, there has been interest in the provision of an accurate gravity type IV administration infusion controller. Two examples are found in U.S. Pat. No. 4,105,028 to Sadlier and U.S. Pat. No. 4,173,224 to Marx. These two patents demonstrate drop size variations due to numerous factors, such as viscosity, rate, etc. These patents suggest two approaches to make their drop recorders and controllers more accurate.
With regard to urinary output monitors, numerous techniques have been devised to monitor urine flow including ultrasonically determining the fluid level and amount of fluid collected, weighing the urine as it is collected in a bag, employing spinning turbines, and other similar techniques.
In intensive care therapy, it is important to accurately monitor the volumetric outflow of urine from a patient in order to facilitate diagnosis of the types of disease states suffered by a patient. Further, it is important to know the urinary output on a volumetrically accurate basis to make clinical judgments, as to the appropriate amount and type of intravenous fluid therapy to be given the patient. Hence, urinary flow rates over varying periods of time become important parameters for the clinician to evaluate.
Thus, there is still a need for a gravity fed IV infusion controller having improved drop size determination techniques and including accurate lensing capabilities to make for a simplified drop collection and determination. Likewise, there is a need for a volumetric urinary output monitor including an optical sensing chamber and an electronic monitor which allows determination of the exact drop volume and flow rates. The present invention is directed toward filling these needs.